I'm a Cowon guy mainly but recently grabbed a Sansa Fuze+ and Rockboxed it for fun. It's incredibly better an experience with good ol' rb and coming from the cowon i9+ with its touchpad controls I wasn't put off by it much.
One thing I thought that would make a nice addition would be to get some use out of the volume rocker buttons when the player is in hold/locked mode.
In most cowon devices you can assign the +/- volume buttons to being prev/skip track when in hold position, unlock the player and they go back to being volume. It's def very handy, I think rockbox would benefit from this feature.
Seeing as the fuze+ has only 3 tactile buttons (volume and on/off) I think the addition of allowing the user tochoose what the volume rocker buttons do would be neat. I might like the - volume button to be play/pause and the + volume to be skip track for example.
Anyway, just my 2 cents.
Bruce